HI All, I'm a bit stumped. I've got a 2007 Subururban LTZ with 5.3 flex fuel, 196K miles. No error codes at present. Occasionally it'll through a P0442 Evap small leak detected. When started cold it will, what I think anyway, is a small backfire through the intake manifold. Just makes a quick pop, misses a second, keeps running. Will do it several times. Once warmed up, it runs perfect. Not misses, no engine light in dash, nothing. I'm wondering if it is something in metering... MAF or O2 Sensors. It's had a new fuel pump in the last few months but same symptoms before and after pump. Issue went away over the summer when it was warm here in KS. Colder it is the worse the problem. Any similar experiences or ideas to fix? Thanks all!

 

Might be idle air control valve needs cleaning.

 

I don't think the 2007 5.3 uses the idle air valve.... Any other thoughts? Timing chain?

BW

 

I dont think the MAF would do this, but you could clean it if you think it might. At 196K it wouldnt hurt to clean it anyhow.

Not really all that familiar with F/F, but does it do this on gasoline only or on E85 ?